Genetic parameters of spontaneous spring ovulatory activity in Merinos d'Arles sheep.

摘要

The study was conducted on sheep kept under the usual pastoral and transhumant management conditions of this breed in southeastern France, and used data for the years 1995, 1996 and 1997. Ovulatory activity was determined from plasma progesterone concentrations in 2 blood samples taken 8-10 days apart. The data set consisted of 1 887 ovulatory activity measurements recorded during 1995-97 on 933 ewes, daughters of 176 rams. The effects of physiological status (hoggets, adult ewes with or without lambing in the previous autumn), age and live weight just before the mating period on ovulatory activity were highly significant. They were fitted in the linear animal model and the threshold sire model used to estimate genetic parameters. On average, 27.9% of ewes exhibited ovulatory activity in April. Age and live weight just before the mating period had a marked positive effect on ovulatory activity; a difference of about 8-9% was observed between extreme classes for these factors. Estimates of heritability (h2) and repeatability of ovulatory activity by the linear model were 0.20±0.04 and 0.30±0.07 respectively. Using the threshold model, h2 was estimated as 0.37.